IMSML Website Article 34/2023: MSN05/2023 - Maintenance and Inspection of Fire Protection System and Appliances, Part 2 of 2, MSC.1/Circ.1270

Main Points of MSC.1/Circ.1270

Aerosol fire-extinguishing systems involve the release of a chemical agent to extinguish a fire by interruption of the process of the fire, see Annex, Section 2. There are two types of aerosol in use:

[1] condensed aerosols are created in pyrotechnical generators through the combustion of the agent charge, see Annex, Section 2.1; and

[2] dispersed aerosols that are not pyrotechnically generated and are stored in containers with carrier agents (such as inert gases or halocarbon agents) with the aerosol released in the space through valves, pipes and nozzles, see Annex, Section 2.2.

Definitions

The defined terms used in this Circular are as follows (ie produced here in verbatim):

[1]’ Aerosol’ is a fire-extinguishing medium consisting of finely divided solid particles of chemicals released into a protected space as either condensed aerosol or dispersed aerosol, Annex, Section 3.

[2]’ Generator’ is a device for creating a fire-extinguishing medium by pyrotechnical means, Annex, Section 4.

[3]’ Efficiency’ coefficient is the percentage (%) of aerosol forming composition actually discharged from a specific aerosol generator. It is determined by comparing the mass loss of a generator after discharge to its beginning mass, see Annex, Section 5.

[4]’ Design’ application density (g/m3) is the mass of an aerosol forming composition per m3 of the enclosure volume required to extinguish a specific type of fire, including a safety factor of 1.3 times the test density, see Annex, Section 6.

[5] ‘Agent ‘is a medium for the purpose of these guidelines, these words are interchangeable, see Annex, Section 7.

Principal Requirements

The testing and application of density of the equipment has to be made in accordance with Appendix 1 and 2 respective, see Annex, Section 8 and 9. Although systems may need to be discharge much quicker, the benchmark is not longer than 120 seconds. The minimum expected ambient temperature using the design density based on the net volume of the protected space, including the casing, will determine the quantity of extinguishing agent for the protected space, see Annex, Section 11.

In particular, The net volume of a protected space is that part of the gross volume of the space, which is accessible to the fire-extinguishing agent, see Annex, Section 11.1. The calculated net volume should include the volume of the bilge, the volume of the casing and the volume of free air contained in air receivers that in the event of a fire may be released into the protected space, see Annex, Section 11.2.

The objects that occupy volume in the protected space should be subtracted from the gross volume of the space include, but are not necessarily limited to: Auxiliary machinery; boilers; condensers; evaporators; main engines; reduction gears; tanks; and trunks, see Annex, Section 11.3.1 to 11.3.8. Subsequent modifications to the protected space that alter the net volume of the space should require the quantity of extinguishing agent to be adjusted, see Annex, Section 11.4.

The discharge of aerosol systems to extinguish a fire could create a hazard to personnel, so no fire suppression system should be used which is carcinogenic, mutagenic or teratogenic at application densities expected during use, see Annex, Section 12. Other potential hazards which should be taken into account include, noise from discharge, turbulence, cold temperature of vapourising liquid, reduced visibility, potential toxicity, thermal hazard, potential toxicity from aerosol generators , as well as eye irritation from direct contact with aerosol particles. All aerosols used should have non-ozone depleting characteristics, see Annex, Section 12.

There should be two separate control systems for releasing the extinguishing medium, accompanied by automatic visual and audible warning of the release into any space where personnel normally work. Alarms should enable to give them time necessary to evacuate the space, not less than 20 seconds before the medium is released, see Annex, Section 12.1. Aerosol should not exceed the appropriate excursion limit for the critical toxic effect as determined by acute inhalation toxicity tests, sue Annex, Section 12.2.

Note:

[a] For application of the No Observed Adverse Affect Level (NOAEL) and exposure under the Physiologically Based Pharmacokinetic (PBPK) or its equivalent, see Annex, Section 12.3;

[b] For usage of inert gas, see Annex, Section 12.4;

[c] For usage of Halocarbon Carrier Gas for concentrations above the Lowest Observed Adverse Effect Level (LOAEL) and the Approximate Lethal Concentration (ALC), see Annex, Section 12.5.

System component should be designed to withstand ambient temperature changes, vibration, humidity, shock, impact, clogging, electromagnetic compatibility and corrosion normally encountered in machinery spaces. In particular, self-activation at a temperature below 250 degrees Celsius should be a design feature in generators in condensed aerosol systems, see Annex, Section 13.

Design and installation standards under Annex, Section 14, should cover the following elements:

[a] Safety, see Annex, Section 14.1;

[b] Storage container design and arrangement, see Annex, Section 14.2;

[c] Agent supply, quantity, quality standards, shelf life and service life of agent and igniter, see Annex, Section 14.3;

[d] Handling and disposal of generator after service life, see Annex, Section 14.4;

[e] Pipes and fitting, see Annex, Section 14.5;

[f] Valves, see Annex, Section 15.6;

[g] Generators / nozzles, see Annex, Section 15.7;

[h] Actuation and control systems, see Section 15.8;

[i] Alarms and indicators, see Annex, Section 15.9;

[j] Enclosure integrity and leakage requirements, see Annex, Section 15.10;

[k] Electrical circuits for pyrotechnic generators, see Annex, Section 15.11;

[l] Design Density Requirements, total flooding quantity, see Annex, Section 15.12;

[m] Agent flow calculation, see Annex, Section 15.13;

[n] Inspection, maintenance, service and testing requirements, see Annex, Section 15.14;

[o] Handling and storage requirements for pyrotechnical components, see Annex, Section 15.15.

Generator/ nozzle type, maximum spacing, maximum installation height and minimum pressure should be within tested limits, see Annex, Section 15. Installations should be limited to the maximum volume tested, see Annex, Section 16. Agent containers stored within a protected space, are required by Annex, Section 17, to be evenly distributed and meet the following:

[a] A manually initiated power release located outside the protected space, see Annex, Section 17.1;

[b] Monitoring of electric power circuits connecting the generators, see Annex, Section 17.2;

[c] There should be widely duplicated and separated pneumatic, electric to hydraulic power circuits connecting the generators, see Annex, Section 17.3;

[d] Electrical circuits within the protected space essential for the release of the system, should be fire resistent according to IEC 60331 standard , or equivalent, see Annex, Section 17.4;

[e] Automatic overpressure release device should be fitted to each dispersed aerosol pressure container, which can safely vent if exposed to the effects of fire, see Annex, Section 17.5;

[f] In the event of damage to generators, electrical circuits and piping (for example through mechanical damage, fire or explosion), there should be one power release line, see Annex, Section 17.6;

[g] Decrease in pressure due to leakage and discharge, should be monitored in dispersed aerosol containers, see Annex, Section 17.7.

There should be counter-measure for significant over or under pressurisation when there is a release of an extinguishing agent in a protected space, see Annex, Section 18. Decomposition of extinguishing agents should be addressed, and not produce health hazards, see Annex, Section 19. Operational test for spare parts, as well as operating and maintenance instruction should be in accordance with the manufacturer’s recommendation, see Annex, Section 20. The temperature profile of the discharge stream should be measured and used to establish a safe minimum distance, see Annex, Section 21. Note that the same should also be done for the casing temperature, see Annex, Section 22. Generators should be separated from escape routes, see Annex, Section 23, and combustible materials, see Annex, Section 24.

Appendix 1

This appendix deals with the test method for fire testing of aerosol fire-extinguishing systems. It provides for the following:

[a] sampling;

[b] method of testing;

[c] extinguishing system;

[d] classification criteria;

[e] the test report.

Appendix 2

This appendix is on the test method for determination of aerosol generator efficiency coefficient, and contains the following:

[a] methodology;

[b] classification criteria.

IMO Corrigendum

MSC.1/Circ.1270 ends with a Corrigendum titled ‘Revised Guidelines for the Approval of Fixed Aerosol Fire-Extinguishing Systems Equivalent to Fixed Gas Fire-Extinguishing Systems, referred to in SOLAS 74, for Machinery Spaces. It contains diagrams for ventilation hatches for the ceiling, closable access door dimensions, and low pressure, low flow concealed heptane spray.

Thank you for reading IMSML Website Article 34/2023

Stay tuned for the next IMSML Website Article 35/2023: MSN06/2023 - Delegation of Responsibilities to Recognised Organisations for Verifying Compliance with the ISM Code and Issuing Documents of Compliance

Signing-off for today,

Dr Irwin Ooi Ui Joo, LL.B(Hons.)(Glamorgan); LL.M (Cardiff); Ph.D (Cardiff); CMILT

Professor of Maritime and Transport Law

Head of the Centre for Advocacy and Dispute Resolution

Faculty of Law

Universiti Teknologi MARA Shah Alam

Selangor, Malaysia

Friday, 20 October 2023

Note that I am the corresponding author for the IMSML Website Articles. My official email address is: uijoo310@uitm.edu.my